1. Field of the Invention
The present invention relates to a storage management system and method, and in particular to a storage management system and method which virtualizes a plurality of storage devices distributed over a network to be managed.
Together with recent highly advanced communication technologies, enormous amounts of information such as storage data are transmitted between a host (application server or user) and one or more storage devices. For this transmission, storage virtualization technology of managing one or more storage devices distributed and arranged over the network as a virtualized single storage device has become the more important.
2. Description of the Related Art
Development of Storage Area Network (SAN)
A DAS (Direct Attached Storage) configuration in which an application server (host) directly connects a storage device such as a disk device or tape drive device to the server itself was conventionally mainstream.
However, in recent years, a SAN technology has been developed by which a plurality of storage devices are connected to the application server through a network and storage devices with large capacity are provided to the server. In this SAN technology, a fiber channel (FC) protocol is generally used as a communication protocol between the application server and the storage devices.
A SAN-specific network device such as an FC switch which switches data transferred by e.g. the FC protocol is also generally used. However, the FC-based network device is more expensive compared with a device for a LAN. For this reason, the SAN has less widespread.
Debut of IP-SAN
Among the communication protocol between the application server and the storage devices in the SAN, some protocols having more affinity for IP have made their debuts in recent years, instead of the FC protocol. One of the protocols especially noticed is an iSCSI (SCSI protocol over the Internet) protocol.
This iSCSI protocol prevents a SCSI (Small Computer Systems Interface) command system from being observed from outside by capsuling a SCSI command, which is a standard of a storage field, and the data with a TCP/IP packet, and enables the storage data to be transferred on an IP network. This protocol enables the storage devices to be directly connected to the IP network.
As a result, a conventional hub, router, switch and the like structuring the LAN/WAN can be used for transferring the storage data, so that a reduction of a facility cost and a management cost by integrating the SAN and the LAN is expected.
Furthermore, the iSCSI protocol has the following advantages (1)-(3):    (1) The application server can read and write data in the same procedure as a conventional procedure for accessing a local storage device without awareness of the iSCSI protocol;    (2) Reading from/writing to a disk is performed per block data in the same way as the conventional SAN, so that a file system such as a NAS (Network Attached Storage) is not required on the storage side;    (3) At present, a transfer rate (1 Gbps) of a gigabit Ethernet does not differ very much from a transfer rate (1 Gbps) of the fiber channel-based SAN. However, since it can be considered that a 10 Gbps Ethernet or a higher-speed Ethernet standard makes its debut in the future, further improvements of transfer performance can be expected.Storage Virtualization
Also, “storage virtualization technology” has made its debut in recent years.
FIG. 17 shows this storage virtualization technology. A storage management device 500, application servers 600_1-600_3 (hereinafter, occasionally represented by a reference numeral 600), a plurality of storage devices such as disk arrays 300_1, 300_2, and a tape device 300_3 (hereinafter, occasionally represented by a reference numeral 300) are mutually connected through a SAN 640.
A plurality of storage devices can be used as a single virtualized storage (storage pool) 350 by the storage virtualization technology.
By a manual setup (see T10) from the storage management device 500, a system manager can divide the virtualized storage 350 into e.g. virtualized storage spaces 351-354, can perform pool assignment of the spaces 351-353 respectively to the servers (hosts) 600_1-600_3, and can leave the space 354 unassigned.
Namely, the virtualized storage pool 350 is prepared by a network connection of the storage devices 300_1-300_3, for example, of a plurality of vendors, so that a physical arrangement of the storage devices 300 can be concealed from the server (or system manager) 600. Also, it becomes possible to flexibly assign and rearrange a storage space independent of the physical arrangement of the storage device 300.
There are some methods for the storage virtualization technology depending on where a conversion/association between the virtualized storage space and an actual storage space is performed.
As a general method, there is a method of performing the conversion/association by a virtualization software within the application server 600. In this method, a volume management software installed in the application server 600 executes the management/assignment of the virtualized storage pool 350. Also, as for the setup/management of the storage virtualization, a method that the system manager inputs/sets up a disk capacity or the like required as a virtual volume on the software is generally adopted, as shown in FIG. 17.
Also, there is a storage management system by which a SAN manager easily performs an arrangement optimization by rearranging the storage space in a plurality of storage devices in a SAN environment (see Patent Document 1).
[Patent document 1] Japanese Patent Application Laid-open No. 2003-140836
Problem (1): Deterioration of Network Transfer Performance
FIG. 18 shows a deterioration example (1) of a network transfer performance, and shows a network in which the storage devices are virtualized in the same way as FIG. 17. Clients 610_1-610_4 and servers (hosts) 600_1 and 600_2 (hereinafter, occasionally represented by a reference numeral 600) of FIG. 18 correspond to the server 600 of FIG. 17. The disk array 300 of FIG. 18 and other storage devices (not shown) correspond to the storage devices 300 (disk arrays 300_1 and 300_2, and tape device 300_3) of FIG. 17. An IP-SAN network 640 composed of routers/switches 400_1-400_4 of FIG. 18 corresponds to the SAN network 640 of FIG. 17.
In this network, the clients 610_1, 610_2, and the server 600_1 belong to a department (business operation) 620_1, while the clients 610_3, 610_4, and the server 600_2 belong to a department 620_2.
The virtualized storages 350_1 and 350_2 composed of the disk arrays 300 and the like are respectively assigned to the departments 620_1 and 620_2.
When the storage virtualization technology is thus introduced on the IP-SAN network 640, storage data between the hosts and the storage devices coexist on the IP-SAN network 640 to be transferred.
Namely, the storage data between different hosts and different storage devices flow on the same link on the IP-SAN network 640. Thus, a shortage of a bandwidth necessary for the storage data transfer and a transfer delay occur (see fault T20), so that the network transfer performance deteriorates.
FIG. 19 shows a deterioration example (2) of the network transfer performance. In FIG. 19, the IP-SAN network 640 is connected to a WAN 650. In this case, not only the storage data (traffic) between the host and the storage devices, but also normal data (traffic) such as normal voice and Web transferred between the host and the WAN 650 flow on the IP-SAN network 640.
Namely, the normal data and the storage data coexist on the link to be transferred. As a result, congestion, a transmission delay and a bandwidth shortage caused by the congestion occur on the IP-SAN network 640, so that the transfer performance deteriorates (see faults T30 and T31).
When a storage redundancy method of RAID (Redundant Arrays of Independent Disks) 5 or the like is applied in this state with a plurality of storage devices distributed over the network using the virtualization technology, for example, a rate reduction of reading/writing data occurs due to the deterioration of the network transfer performance.
Problem (2): Complicated Virtual Storage Management
When the virtual volume is prepared for the host (server) with the storage virtualization technology, it is required to appropriately determine a used space of disk from the storage devices distributed over the network for a disk capacity required by the host. Namely, it is required to determine a disk space based on a disk utilization and an available space within the storage device 300. By the virtualization method presently performed, a manger estimates an available status of a disk and determines a disk capacity used for the virtual volume and the storage device 300, so that an immediate virtualization is impossible.
Furthermore, in order to perform the virtualization on the IP-SAN network 640, as already mentioned, it is required to determine an appropriate transfer path of the storage data based on a position of a selected disk (storage device) and the usage (utilization) state of the IP-SAN network 640. Also, it is required to set up the determined path in the host and the network device. The manual setup by a manager is a very complicated operation, so that an immediate path determination and its setup are difficult. The path determination and the path setup are not mentioned in the storage management system shown in the above-mentioned patent document 1.